| With the rapid development of the wireless communication technology, the wireless products are more closely bound up with people's life. As the power amplfier is the basal component of wireless communication, The design methods of power amlplifier are renovating consistently. Wide bandwidth, good linearity and high efficiency are the purposes of the power amplifier design. As the complex digital modulations which cause the varied envelopes are using popularly, the linearity is the most emergent challenge. Practices have proven that the feedforward linearity technology is the most popupar and potential. Therefore this thesis states a low cost linear power amplifier design using feed- forward technology. The power amplifier works at the downlink of CDMA networks.Firstly the author introduces the importance of the good linearity of power amplifier and the current prevailing power amplifier design technologies. Through comparison, the author concludes the advantages of the feedforward linearity technology. Secondly, the article describes key characters of the power amplifier, classifications of power amplifier and estimation of power amplifier's stabilization. Thirdly the thesis states the theory of feedforward linearity technology, the system design scheme and detailed circuit units, including the choices of chips, design of input unit, design of power supply unit, design of detecting circuit, design of automatic level control, power amplifier designs and so on. Finally the author describes the assembling principles, debugging methods and the testing results. The maximum output power of the power amplifier is 45dBm; IMD3 is less than -55dBc; and the ACPR are better than -47dBc and -61dBc. The system is still requiring optimizing which is the author's following work.The author's key works include: using ADS to simulate the power amplifier transistors; design the entire circuits of the feedforward system; debugging and measuring. |
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